CN117425787A

CN117425787A - Harmonic gear device

Info

Publication number: CN117425787A
Application number: CN202180098242.7A
Authority: CN
Inventors: 今川丰
Original assignee: Shin Kong Reducer Co ltd
Current assignee: Shin Kong Reducer Co ltd
Priority date: 2021-09-16
Filing date: 2021-09-16
Publication date: 2024-01-19
Also published as: JP7039097B1; KR20240007653A; TW202314140A; WO2023042331A1; JPWO2023042331A1

Abstract

The harmonic gear device is provided with: an internal gear section, a harmonic generation section, a flexible gear section (20) having an external gear, and an output section (40) that rotates together with the flexible gear section (20). The flexible gear portion (20) has a first annular portion (22) integrally formed with the external gear from the same material as the external gear. The output section (40) has a second annular section (41) that faces the first annular section (22) in the radial direction around the Axis (AX). The second annular portion (41) is provided with a transmission tooth (6 a) protruding along the radial direction, and the first annular portion (22) is provided with a recess (6 b) into which the transmission tooth (6 a) is inserted. The width of the recess (6 b) in the circumferential direction is wider than the width of the transmission tooth (6 a) in the circumferential direction, allowing relative displacement of the flexible gear portion (20) and the output portion (40) in the circumferential direction. A plurality of transmission pairs are provided as pairs of transmission teeth (6 a) and recesses (6 b), and are arranged in the circumferential direction.

Description

Harmonic gear device

Technical Field

The present disclosure relates to a harmonic gear device.

Background

As the speed reducer, there is a speed reducer using a harmonic gear device. For example, the harmonic gear device described in patent document 1 includes: a flexible gear portion fitted to a harmonic generation portion as an input rotary element; an internal gear portion engaged with the flexible gear portion; and an output plate portion that rotates according to the rotation of the flexible gear portion. The output plate portion is an output element for decelerating rotation in the harmonic gear device. The flexible gear portion is provided with a plurality of transmission pin portions arranged in the circumferential direction. The transmission pin section includes: a transfer pin body extending along a rotational axis of the output member; and a transmission roller rotatably supported by the transmission pin body. The output plate portion is provided with a hole into which the transmission roller is inserted, and allows displacement of the transmission pin portion in at least one of the circumferential direction and the radial direction at the time of rotation transmission.

Patent document 2 describes a twin harmonic gear device provided with a pair of first and second internal gears as a configuration corresponding to the internal gear portion. In this device, an external gear corresponding to the flexible gear portion includes: the first external teeth meshed with the first internal gear, the second external teeth meshed with the second internal gear, and the rim connecting the two are integrally formed. The first internal gear is a fixed element that does not rotate, while the second internal gear is an output element of a rotatable harmonic gear device. That is, the twin harmonic gear device transmits the rotation power of the external gear from the second external teeth to the second internal gear to obtain a reduced rotation output.

Prior art literature

Patent literature

Patent document 1: japanese patent application laid-open No. 2018-194150

Patent document 2: japanese patent No. 6552571

Disclosure of Invention

(problem to be solved by the invention)

Here, as transmission points for transmitting force from the rotating flexible gear portion to the output element, a plurality of virtual points arranged in a circumferential direction around the rotation axis of the output element are considered. The vector of the force applied from the rotating flexible gear portion to each virtual point is not uniformly directed in the circumferential direction, but is shifted in phase depending on the point due to the flexibility of the flexible gear portion, the cam shape of the harmonic generation portion, and the like. In this way, in the flexible gear portion including many vectors of force causing the phase shift, there is a problem that wasteful stress is generated which does not contribute to torque for rotating the output element, and wasteful torsional force is applied.

In the structure described in patent document 2, the wasteful torque cannot be completely released, and the flexible gear portion may be broken, and the device may malfunction. In the device described in patent document 2, the number of teeth of the second internal gear as the output element is different from the number of teeth of the second external gear of the flexible gear portion. Because of the difference in the number of teeth, when the harmonic generation section rotates, the meshing position of the second external teeth and the second internal tooth gear moves in the circumferential direction, and therefore the relative position of the flexible gear section and the output member deviates from a desired position, and there is a possibility that the device may malfunction. In addition, the structure of the duplex type harmonic gear device is complicated.

On the other hand, the device described in patent document 1 can suppress the generation of the wasteful torque. However, the structure of this device is also complicated, and it is not easy to mount the transmission pin portion to the flexible gear portion with high accuracy. In addition, the flexible gear portion may become fragile due to the processing of attaching the transmission pin portion to the flexible gear portion.

An object of the present disclosure is to provide a harmonic gear device capable of reducing the risk of failure with a compact structure.

(means for solving the problems)

In order to achieve the above object, a harmonic gear device according to the present disclosure includes:

An internal gear portion having an internal gear formed along an inner peripheral surface;

a harmonic generation unit having a cam unit that rotates about an axis in response to a rotational input;

a flexible gear portion having an annular external gear formed along an outer peripheral surface with fewer teeth than the internal gear and having an inner peripheral side fitted into the harmonic generation portion; and

an output portion that rotates with the flexible gear portion relative to the internal gear portion,

the cam part has N pole parts, N is an integer of 2 or more, the N pole parts are positioned at equally spaced positions in the circumferential direction with the axis as the center, the cam part enables the external gear to be meshed with the internal gear at N positions,

the flexible gear portion has a first annular portion integrally formed with the external gear from the same material as the external gear, located closer to the output portion than the external gear in a direction along the axis,

the output section has a second annular section opposed to the first annular section in a radial direction centering on the axis,

a transmission tooth protruding along the radial direction is provided on one of the first annular portion and the second annular portion, a recess portion into which the transmission tooth is inserted is provided on the other of the first annular portion and the second annular portion,

The width of the recess in the circumferential direction is wider than the width of the transmission tooth in the circumferential direction, the recess allows relative displacement of the flexible gear portion and the output portion in the circumferential direction,

the pairs of the transfer teeth and the recesses, that is, the transfer pairs, are plural and arranged in the circumferential direction.

(effects of the invention)

According to the present disclosure, it is possible to provide a harmonic gear device capable of reducing the risk of failure with a compact structure.

Drawings

Fig. 1 is a schematic cross-sectional view of a main structure of a harmonic gear device according to an embodiment of the present disclosure.

Fig. 2 is a view of the main structure of the harmonic gear device according to the above embodiment as viewed from the axial direction, and is a view showing the case where the number of poles of the cam portion is 2.

Fig. 3 is a view showing a part of the outer peripheral surface of the flexible gear portion of fig. 2.

Fig. 4 is a diagram for explaining the arrangement and function of the transfer pair according to the above embodiment.

Fig. 5 is a view of the cam portion and the flexible gear portion as viewed from the axial direction, and is a view showing a case where the number of poles of the cam portion is 3.

Fig. 6 is a view of the cam portion and the flexible gear portion as viewed from the axial direction, and is a view showing a case where the number of poles of the cam portion is 4.

Fig. 7 is a diagram for explaining the arrangement and function of the transfer pair according to modification 1.

Fig. 8 is a diagram showing the shape of a transmission pair according to modification 2.

Detailed Description

An embodiment of the present disclosure will be described with reference to the accompanying drawings.

As shown in fig. 1, the harmonic gear device 100 is assembled to an industrial robot 200. The robot 200 is constituted by a vertical multi-joint robot, for example. The robot 200 includes: the first arm 211, the second arm 212 connected to the first arm 211 via the harmonic gear device 100, the motor 213, and a controller not shown. The motor 213 is constituted by a servo motor or the like, and operates under control of a controller. The controller rotationally drives the second arm 212 via the motor 213 and the harmonic gear device 100 built in the first arm 211, thereby performing positioning control, angle control, and rotational speed control of the second arm 212 with respect to the first arm 211.

The harmonic gear device 100 includes: a harmonic generation unit 10, a flexible gear unit 20, an internal gear unit 30, an output unit 40, and a support unit 50.

In fig. 1, a cross section showing a part of the structure is omitted from the viewpoint of easy observation, and a structure other than the harmonic gear device 100 is shown by a phantom line. In the following, when the configuration of the harmonic gear device 100 is described, the right side in fig. 1 may be referred to as an input side (illustrated Si) and the left side may be referred to as an output side (illustrated So).

The harmonic generation unit 10 includes: a cylindrical shaft portion 11, a cam portion 12 integrally formed with the cylindrical shaft portion 11, and a wave bearing 13.

The input-side end of the cylindrical shaft portion 11 is rotatably supported by a bearing B1, and the output-side end of the cylindrical shaft portion 11 is rotatably supported by a bearing B2. The bearing B1 is provided in the stationary portion 211a that is stationary with respect to the first arm 211. The bearing B2 is provided on the inner peripheral surface of the output portion 40. The bearings B1 and B2 are constituted by ball bearings, for example. Thereby, the cylindrical shaft portion 11 is supported rotatably about the axis AX with respect to the first arm 211. The rotation power of the motor 213 is transmitted to the cylindrical shaft portion 11 via a known transmission mechanism. The transmission mechanism may be any gear mechanism, belt mechanism using a timing belt and pulleys, or the like.

The cam portion 12 is provided so as to protrude from the outer peripheral surface of the cylindrical shaft portion 11 in the outer radial direction. The cam portion 12 is provided at a position adjacent to the bearing B1 in a direction along the axis AX (hereinafter also referred to as "axial direction"). The cam portion 12 has N (N is an integer of 2 or more) pole portions located at equally spaced positions in the circumferential direction around the axis AX. Hereinafter, the number of poles of the cam portion 12 will be referred to as the number of poles. For example, as shown in fig. 2, the cam portion 12 in the case where the number of poles is n=2 is elliptical as viewed from the axial direction.

As shown in fig. 1 and 2, the wave bearing 13 has: an inner ring 13i fixed to the outer peripheral surface of the cam portion 12, a flexible outer ring 13o, and a plurality of balls 13b interposed between the inner ring 13i and the outer ring 13o in a rolling state. The inner ring 13i may be formed by a portion including the outer peripheral surface of the cam portion 12.

The flexible gear portion 20 is formed of a metal material such as special steel to have flexibility, and includes: an external gear 21, a first annular portion 22, and a connecting portion 23. The external gear 21, the first annular portion 22, and the connecting portion 23 are integrally formed of the same material.

The external gear 21 has a plurality of teeth 21a formed along the outer peripheral surface and is formed in a ring shape, and the inner peripheral side is fitted into the outer ring 13o of the harmonic generation unit 10. The plurality of teeth 21a in the external gear 21 are arranged at regular intervals in the circumferential direction. The number of teeth T of the external gear 21, which is the number of teeth 21a, is smaller than the number of teeth T of the internal gear 31, which is the number of teeth 31a, which will be described later. For example, when the number of poles of the cam portion 12 is N, the relationship between the number of teeth T and the number of teeth T is set to "t=t+n". For example, in the case of n=2, the relationship of "t=t+2" holds.

The first annular portion 22 is an annular portion located closer to the output portion 40 than the external gear 21 in the axial direction of the external gear 21. As shown in fig. 4, the first annular portion 22 is provided with a recess 6b into which the transmission-receiving teeth 6a provided in the output portion 40 are inserted. By the engagement of the transmission teeth 6a with the concave portions 6b, the power of the flexible gear portion 20 is transmitted to the output portion 40. The concave portions 6b are provided in the same number as the transmission teeth 6a, and are provided in plurality along the circumferential direction centered on the axis AX. The transmission teeth 6a and the concave portions 6b will be described in detail later.

The connecting portion 23 connects the external gear 21 to the first annular portion 22 having a smaller diameter than the external gear 21. As shown in fig. 1, the connecting portion 23 is inclined from the external gear 21 toward the first annular portion 22 and closer to the axis AX.

Fig. 2 and 3 show a part of the first annular portion 22 of the flexible gear portion 20. Fig. 3 is a view of a part of the outer peripheral surface of the flexible gear portion 20 as seen from the direction of 0 ° shown in fig. 2.

The inner gear portion 30 is formed of a metal material to have rigidity and is fixed to the inner side of the first arm 211. The internal gear portion 30 has an internal gear 31 partially meshed with the external gear 21 of the flexible gear portion 20 bent at the cam portion 12. The internal gear 31 has a plurality of teeth 31a formed along the inner circumferential surface and is formed in a ring shape. The plurality of teeth 31a of the internal gear 31 are arranged in the circumferential direction at regular intervals.

The internal gear portion 30 is formed in a substantially cylindrical shape. On the input side of the harmonic gear device 100, the internal gear portion 30 is opposed to the stationary portion 211a provided with the bearing B1 in the axial direction. An annular groove centered on the axis AX is provided at a portion of the internal gear portion 30 facing the stationary portion 211a, and an O-ring 71 is fitted into the groove. The internal gear portion 30 is fixed to the stationary portion 211a by a screw 81 along the axial direction.

The output portion 40 rotates with the flexible gear portion 20 relative to the inner gear portion 30. The output portion 40 is supported by the support portion 50 so as to be rotatable about the axis AX with respect to the internal gear portion 30. The output portion 40 is formed of, for example, a metal material into a rigid ring shape.

The output unit 40 includes, in a radial direction (hereinafter, also simply referred to as a "radial direction") centered on the axis AX: a second annular portion 41 opposed to the first annular portion 22; and a supported portion 42 which is located on the output side of the second annular portion 41 and is supported by the support portion 50. As shown in fig. 4, the second annular portion 41 of the present embodiment is located on the inner peripheral side of the first annular portion 22 of the flexible gear portion 20. The second annular portion 41 is provided with a transmission tooth 6a.

The support portion 50 is constituted by, for example, a cross roller bearing, and includes: an outer ring 51 fixed to the inner gear portion 30; and an inner ring 52 fixed to the supported portion 42 of the output portion 40. The outer race 51 is fixed to the inner gear portion 30 by a screw 82. The inner race 52 is fixed to the supported portion 42 by a screw 83. Both screws 82, 83 are along the axial direction.

On the output side of the harmonic gear device 100, the internal gear portion 30 is axially opposed to the outer ring 51 of the support portion 50. The internal gear portion 30 includes: an insertion hole 32 formed along the axial direction for insertion of the screw 82; and a determining portion 33 located between the insertion hole 32 and the first annular portion 22. The portion of the determining portion 33 facing the outer ring 51 in the axial direction has an annular groove 33a centered on the axis AX. An O-ring 72 is fitted into the annular groove 33a. The O-ring 72 and the O-ring 71 described above prevent water from entering from the outside of the device, oil from leaking from the inside of the device, and the like.

In this embodiment, the output unit 40 is connected to the second arm 212, which is a load of the harmonic gear device 100, via the inner ring 52 of the support unit 50. Thereby, the second arm 212 rotates around the axis AX with the rotation of the output unit 40. The manner of supporting the output unit 40 by the supporting unit 50 and the method of connecting the output unit 40 to the load can be arbitrarily changed.

As shown in fig. 1, the first annular portion 22 of the flexible gear portion 20 and the second annular portion 41 of the output portion 40 are located between the support portion 50 and the cam portion 12 in the axial direction. The transmission teeth 6a of the second annular portion 41 are pressed by the concave portion 6b of the first annular portion 22 in a circumferential direction (hereinafter, also simply referred to as "circumferential direction") centered on the axis AX, whereby the output portion 40 rotates together with the flexible gear portion 20.

The transmission teeth 6a are configured to transmit the power of the flexible gear portion 20 to the output portion 40. The transmission teeth 6a protrude from the outer peripheral surface of the second annular portion 41 in the radial direction, and are inserted into the recess 6b in the first annular portion 22.

The recess 6b is provided on the inner peripheral surface of the first annular portion 22. As shown in fig. 4, the width of the recess 6b in the circumferential direction is wider than the width of the transmission tooth 6a in the circumferential direction (the direction indicated by symbol C in fig. 2 and 3). Thereby, the concave portion 6b allows relative displacement in the circumferential direction with the transmission teeth 6a (i.e., relative displacement in the circumferential direction of the flexible gear portion 20 and the output portion 40). The width of each of the transmission teeth 6a and the concave portions 6b in the circumferential direction may be set so that a first pair 61 and a second pair 62, which will be described later, can appear as a pair of the transmission teeth 6a and the concave portions 6b. A plurality of transmission pairs, which are pairs of the transmission teeth 6a and the concave portions 6b, are provided along the circumferential direction and are arranged at equal intervals in the circumferential direction.

(regarding the deceleration action)

Next, a deceleration operation of the harmonic gear device 100 will be described. The number N of poles of the cam portion 12 is arbitrary as long as it is an integer of 2 or more, but here, a case where the cam portion 12 is n=2 and has an elliptical shape will be described.

When the motor 213 is operated under the control of the controller of the robot 200, the rotational power of the motor 213 is transmitted to the cam portion 12 of the harmonic generation unit 10 via a transmission mechanism, not shown, and the cam portion 12 rotates at a relatively high speed around the axis AX.

Here, for ease of explanation, as shown in fig. 2, the cam portion 12 before the start of rotation is in the initial position where the major axis of the elliptical shape coincides with the axis passing through 0 ° and 180 °. The cam portion 12 in the initial position causes the external gear 21 of the flexible gear portion 20 to mesh with the internal gear 31 of the internal gear portion 30 at meshing positions corresponding to two portions of 0 ° and 180 ° of the two pole portions. The angle shown in the drawing is an angle centered on the axis AX, and the angle increases in the clockwise direction with the direction of 12 points being 0 °. The cam portion 12 is configured to rotate in a clockwise direction.

When the cam portion 12 rotates by an angle α in the clockwise direction from the initial position, θ= {360× (T-T)/T } ×α/360 ° = (α/T) ×n holds when the angle by which the flexible gear portion 20 rotates in the counterclockwise direction with respect to the internal gear portion 30 is set to θ. When the cam portion 12 having the number of poles n=2 is used, the difference in the number of teeth between the internal gear 31 and the external gear 21 is T-t=n=2, and therefore θ= (α/T) ×2 holds. For example, when the cam portion 12 rotates 90 °, the flexible gear portion 20 rotates counterclockwise by an angle θ= (90 °/T) ×2, which corresponds to 1/4 (=90 °/360 °) of the difference "2" of the number of teeth, that is, 1/2 of the number of teeth.

In this way, the flexible gear portion 20 is elastically deformed according to the rotation of the cam portion 12, and the meshing position with the internal gear portion 30 is sequentially moved. When the cam portion 12 rotates 360 °, the flexible gear portion 20 rotates counterclockwise by an angle θ= (360 °/T) ×2, which corresponds to the difference "2" in the number of teeth. Thereby, the rotational speed of the output portion 40 that moves rotationally with the flexible gear portion 20 with respect to the cam portion 12 is decelerated at a reduction ratio of i= (T-T)/T. That is, according to the harmonic gear device 100, the load (in this example, the second arm 212) connected to the output unit 40 can be rotationally controlled with high accuracy by using the output decelerated at the above-described reduction ratio i. The reduction ratio i is arbitrary, but can be set to a level of 1/30 to 1/320, for example.

The case where the number of poles N is n=2 was described above, but the same method is considered for the case where N is equal to or greater than 3, and thus will be collectively described herein. When the number of poles N is equal to or greater than 3, the cam portion 12 has a positive N-sided shape as viewed from the axial direction, and has a curved surface shape that gradually expands in the outer circumferential direction between each pole portion and the adjacent pole portion, for example. Fig. 5 shows a case where the number of poles N is 3, and fig. 6 shows a case where the number of poles N is 4. Although not shown, the same can be done for the case where N is not less than 5.

The external gear 21 of the flexible gear portion 20 is bent at the cam portion 12 having N poles via the wave bearing 13, and is meshed with the internal gear 31 of the internal gear portion 30 at N positions. When the number of poles of the cam portion 12 is N, the relationship between the number of teeth T of the external gear 21 (hereinafter, also referred to as the number of teeth T of the flexible gear portion 20) and the number of teeth T of the internal gear 31 (hereinafter, also referred to as the number of teeth T of the internal gear portion 30) is set to be "t=t+n".

Further, for example, when the cam portion 12 rotates 360 ° in the clockwise direction, the flexible gear portion 20 moves by N teeth in the counterclockwise direction. That is, when the number of poles of the cam portion 12 is N, the flexible gear portion 20 moves by 1 tooth with respect to the internal gear portion 30 when the cam portion 12 rotates by an angle of (360 °/N). When the number of poles of the cam portion 12 is N, the rotational speed of the output portion 40 fixed to the flexible gear portion 20 with respect to the cam portion 12 is decelerated at a reduction ratio of i= (T-T)/t=n/T.

As described above, in the harmonic gear device 100, when the cam portion 12 of the harmonic generation unit 10 rotates in accordance with the rotational input from the motor 213, the meshing positions of the two gears of the flexible gear portion 20 and the internal gear portion 30 move in the circumferential direction, and the flexible gear portion 20 rotates in the opposite direction to the cam portion 12 with respect to the internal gear portion 30 in accordance with the difference in the number of teeth of the two gears, regardless of whether the number of poles N of the cam portion 12 is set to n=2 or n+.3.

(regarding the transfer teeth 6a and the concave portions 6 b)

Next, the transmission teeth 6a and the concave portions 6b will be described. Fig. 4 shows an example of arrangement of the transmission teeth 6a and the concave portions 6b, which is preferable in the case where the number of poles of the cam portion 12 is n=2.

In fig. 4, the outer periphery of the flexible gear portion 20 and the output portion 40 is shown in a graph (hereinafter referred to as a relative displacement graph) showing relative displacement between the transmission teeth 6a and the concave portion 6b in a range of 0 ° to 180 ° when the cam portion 12 having a pole number n=2 rotates about the axis AX according to the operation of the motor 213.

As can be seen from a relative displacement diagram in fig. 4, the positions of the transmission teeth 6a with respect to the concave portions 6b are different at each position where the transmission teeth 6a are provided. This is because the phase shift described in the foregoing problem occurs. The harmonic gear device 100 according to the present embodiment reduces the occurrence of unnecessary stress caused by the phase shift and which does not contribute to the rotation of the output unit 40 by the action of the transmission teeth 6a and the recesses 6b described below, and rotates the output unit 40 with good transmission efficiency.

In the example shown in fig. 4, 16 transmission teeth 6a arranged at equal intervals in the circumferential direction are provided in the second annular portion 41 of the output portion 40. Further, the first annular portion 22 of the flexible gear portion 20 is provided with 16 concave portions 6b into which the respective teeth of the 16 transmission teeth 6a are inserted. That is, in the example of fig. 4, 16 (=8×n) pairs, which are pairs of the transmission teeth 6a and the concave portions 6b, are arranged at intervals of 360 °/16 (=22.5 °) in the circumferential direction.

As shown in the relative displacement diagram of fig. 4, in a state in which the transmission tooth 6a in the transmission pair located in the 0 ° direction is located at the center in the circumferential direction of the recess 6b, the transmission tooth 6a located in the 90 ° direction and the transmission tooth 6a located in the 180 ° direction are located at the centers in the circumferential direction of the respective corresponding recesses 6 b. The transmission teeth 6a located in each direction of 0 °, 90 °, 180 ° do not contact the corresponding concave portions 6b in the circumferential direction, and therefore do not contribute to the rotation of the output portion 40.

Hereinafter, a transmission pair in which the transmission teeth 6a are located at the center of the concave portion 6b in the circumferential direction, such as the transmission pair located in each direction of 0 °, 90 °, 180 ° in fig. 4, is referred to as a first state transmission pair. That is, the transmission of the first state does not contribute to the rotation of the output unit 40.

On the other hand, in the state where the transmission pair in the first state is located in each direction of 0 °, 90 °, 180 °, the transmission tooth 6a located in the direction of 45 ° is located at one end (clockwise end in the drawing) of the inserted recess 6 b. In this state, the transmission tooth 6a located in the 135 ° direction is located at the other end (the end in the counterclockwise direction in the drawing) of the inserted recess 6b in the circumferential direction. When the cam portion 12 rotates clockwise, the transmission teeth 6a located in the 45 ° direction come into contact with the concave portions 6b of the flexible gear portion 20 moving counterclockwise in the circumferential direction, and thus the rotation of the output portion 40 is facilitated. When the cam portion 12 rotates counterclockwise, the transmission teeth 6a located in the 135 ° direction come into contact with the concave portions 6b of the flexible gear portion 20 that moves clockwise in the circumferential direction, and thus contribute to the rotation of the output portion 40.

Hereinafter, a transmission pair in which the transmission teeth 6a are in contact with the concave portions 6b in the circumferential direction, such as the transmission pair located in each direction of 45 ° and 135 ° in fig. 4, is referred to as a second state transmission pair. That is, the transmission pair of the second state contributes to the rotation of the output section 40.

The transmission pair in each direction of 22.5 °, 67.5 °, 112.5 °, 157.5 ° is a transmission pair in a halfway state of transition from one of the first state and the second state to the other. The transmission pair in this intermediate state does not contribute to the rotation of the output unit 40 because the transmission teeth 6a and the concave portions 6b do not contact each other in the circumferential direction.

The behavior of the transmission teeth 6a and the concave portions 6b in the respective ranges of 180 ° to 360 ° is the same as the behavior of the transmission teeth 6a and the concave portions 6b in the ranges of 0 ° to 180 °. That is, at each position having a center angle of 45 ° with respect to the axis AX, the transmission pair of the first state and the transmission pair of the second state alternately appear. The relative displacement diagram of fig. 4 is statically shown, but the transmission pair of the first state is shifted to the transmission pair of the second state via the intermediate state according to the rotation of the flexible gear portion 20. In contrast, the transfer pair of the second state transitions to the transfer pair of the first state via the intermediate state.

The following summarizes the transfer pairs illustrated in fig. 4.

When the number of poles of the cam portion 12 is n=2, the flexible gear portion 20 moves by one tooth with respect to the internal gear portion 30 when the cam portion 12 rotates (360 °/2) by an angle. In this way, the transmission pairs of the first state and the transmission pairs of the second state alternate every 180 °/4=45° within the range of the rotation angle of the cam portion 12 for moving the flexible gear portion 20 by one tooth with respect to the internal gear portion 30, that is, 180 °. The 180 ° range of transfer pairs includes: a first pair 61 having a transmission tooth 6a located at one end of the recess 6b in the circumferential direction; and a second pair 62 whose transfer teeth 6a are located at the other end of the recess 6b in the circumferential direction.

In the relative displacement diagram of fig. 4, the first pair 61 is a transmission pair located in the 45 ° direction, and the second pair 62 is a transmission pair located in the 135 ° direction. When this is considered in the range of 360 °, the 16 transfer pairs include 2 first pairs 61 arranged at equal intervals in the circumferential direction and 2 second pairs 62 arranged at equal intervals in the circumferential direction. Within a range of 360 deg., the first pair 61 and the second pair 62 are alternately present every 90 deg..

In fig. 4, an example in which 8×n=16 transfer pairs are provided is shown, but the transfer pairs (4×n) may be omitted from the portion corresponding to the intermediate transfer pair in fig. 4.

The above idea is not limited to the case of n=2, and can be generalized. Therefore, the case where the number of poles of the cam portion 12 is N (an integer of 2 or more) and the number of transmissions is (4×n) will be described. Here, (4×n) pieces are selected as the number of transmission pairs in which the intermediate state is omitted for easy understanding of the explanation. The transfer pairs are arranged at equal intervals in the circumferential direction.

When the cam portion 12 having the number of poles N rotates by an angle of (360 °/N), the flexible gear portion 20 moves by one tooth amount with respect to the inner gear portion 30. In this way, the transmission pairs in the first state and the transmission pairs in the second state alternate at intervals of 360 °/(4×n) within the range of the rotation angle of the cam portion 12 (360 °/N) for moving the flexible gear portion 20 by one tooth with respect to the internal gear portion 30. The transmission pair in this range (360 °/N) includes a first pair 61 and a second pair 62. When this is considered in the range of 360 °, the (4×n) transfer pairs include N first pairs 61 arranged at equal intervals in the circumferential direction and N second pairs 62 arranged at equal intervals in the circumferential direction. Further, the first pair 61 and the second pair 62 exist alternately every 360 °/(2×n).

As described above, the transmission pairs in the first state and the transmission pairs in the second state alternately appear, and the relative displacement of the transmission teeth 6a and the concave portions 6b in the circumferential direction can be absorbed by a so-called cam system. Therefore, according to the harmonic gear device 100, the occurrence of unnecessary stress that does not contribute to the torque for rotating the output unit 40 in the flexible gear unit 20 and the output unit 40 can be reduced, and the application of unnecessary torsional force to the flexible gear unit 20 can be reduced.

In addition, when the flexible gear portion 20 bent at the cam portion 12 is rotationally moved relative to the internal gear portion 30, the flexible gear portion 20 moves while meshing with the internal gear portion 30, and thus, a pulsation in the radial direction accompanies.

Here, fig. 4 corresponds to the following state: the flexible gear portion 20 is engaged with the internal gear portion 30 at two positions of 0 ° and 180 ° corresponding to the pole portions of the cam portion 12. That is, the flexible gear portions 20 shown in fig. 2 and 4 respectively correspond. In the case of the polar portions of the cam portion 12 at 0 ° and 180 °, the transfer teeth 6a are separated from the concave portions 6b in the radial direction in the transfer pair in the directions of 0 ° and 180 °. At this time, in the transmission pair in the 90 ° and 270 ° directions, the transmission tooth 6a is closest to the recess 6b in the radial direction. When the transmission teeth 6a and the concave portions 6b are closest to each other in the radial direction, the transmission teeth 6a and the concave portions 6b may or may not be in contact with each other in the radial direction.

In the transmission pair between 0 ° and 90 °, the radial distance between the transmission tooth 6a and the recess 6b becomes narrower as approaching 90 °. In the transmission pair between 90 ° and 180 °, the radial distance between the transmission tooth 6a and the recess 6b gradually becomes wider as approaching 180 °. The relationship is also the same in the range of 180 ° to 360 °.

As described above, at least in the two transmission pairs located at positions corresponding to the poles of the cam portion 12, the transmission teeth 6a are separated from the concave portions 6b in the radial direction. Further, the first annular portion 22 allows displacement in the radial direction with respect to the second annular portion 41. The above idea can be generalized not limited to n=2. In the harmonic gear device 100 having N poles of the cam portion 12, at least in N transmission pairs located at positions corresponding to the poles of the cam portion 12, the transmission teeth 6a are separated from the concave portions 6b in the radial direction. Further, the first annular portion 22 allows displacement in the radial direction with respect to the second annular portion 41.

In the harmonic gear device 100 of the present embodiment, the radial displacement of the first annular portion 22 with respect to the second annular portion 41 can be allowed, and therefore the aforementioned radial pulsation can be absorbed. With this configuration, the useless stress can be reduced. The plurality of transmission teeth 6a are set to a shape that does not separate from the concave portion 6b in any of the first state, the second state, and the intermediate state, respectively.

In addition, the transmission pairs of the second state include the first pair 61 and the second pair 62 arranged at equal intervals in the circumferential direction. This allows the flexible gear portion 20 to efficiently transmit the force in the circumferential direction to the output portion 40.

As a result, according to the harmonic gear device 100 of the present embodiment, the mechanical loss generated when the flexible gear portion 20 and the output portion 40 are completely fixed can be significantly reduced, and good transmission efficiency can be achieved. In addition, breakage of the flexible gear portion 20 can be suppressed.

Further, since the output points (i.e., the positions where the transmission pairs are provided) at which the force is transmitted from the flexible gear portion 20 to the output portion 40 can be uniformly dispersed in the circumferential direction, the load at each of the meshing positions of the flexible gear portion 20 and the internal gear portion 30 can be reduced, and as a result, the output portion 40 can be rotated with high torque.

The number of transfer pairs is not limited to (4×n). The number of transfer pairs can be arbitrarily changed according to the number of N.

For example, when the number of poles N of the cam portion 12 is n=8, the transmission pairs in the first state and the transmission pairs in the second state alternately appear in the range of (360 °/N) =45° which is the rotation angle of the cam portion 12 for moving the flexible gear portion 20 by one tooth relative to the internal gear portion 30 when the transmission pairs are (4×n) =32. When this is considered in the range of 360 °, the 32 transfer pairs include 8 first pairs 61 arranged at equal intervals in the circumferential direction and 8 second pairs 62 arranged at equal intervals in the circumferential direction.

However, when the first pair 61 and the second pair 62 are 4, respectively, it is considered that it is sufficient to stably rotate the output section 40, and therefore, the transfer pairs may be set to (2×n) =16. In addition, it is considered that the following structure can be realized not only in the case where n=8: the transmission pairs are set to the number of (2×n), and N first pairs 61 and second pairs 62 are provided, respectively, whereby all the transmission teeth 6a contribute to the rotation of the output section 40. Further, the number of transfer pairs may be set irrespective of the number of N. For example, when 16 transfer pairs are arranged at equal intervals in the circumferential direction, and at least 4 or more pairs of the first pair 61 and the second pair 62 are provided, respectively, the output section 40 can be rotated stably regardless of the number of N. In this way, the output portion 40 provided with the transmission teeth 6a can be shared regardless of the number N of poles of the cam portion 12, and therefore, the manufacturing efficiency can be improved.

As described above, by setting the number of transmission pairs to (2×n) or setting the number of transmission pairs to a fixed value (for example, 16) irrespective of the number of N, the harmonic gear device 100 can reduce unnecessary stress by the same action as described above, and achieve good transmission efficiency.

In the first pair 61, the "one end of the transmission tooth 6a in the circumferential direction of the concave portion 6 b" may be any one as long as the transmission tooth 6a is in contact with or in close proximity to the one end of the concave portion 6b in the circumferential direction. Similarly, in the second pair 62, the "transmission tooth 6a is located at the other end of the recess 6b in the circumferential direction" may be any type as long as the transmission tooth 6a is in contact with or in close proximity to the other end of the recess 6b in the circumferential direction. That is, the first pair 61 and the second pair 62 may be configured to be capable of directly pressing the transmission teeth 6a in the circumferential direction through the concave portions 6b when the flexible gear portion 20 moves toward the transmission teeth 6 a.

The plurality of transmission pairs are so-called "arranged at equal intervals in the circumferential direction", and any state may be used as long as the plurality of transmission teeth 6a arranged at equal intervals in the circumferential direction are inserted into the corresponding plurality of concave portions 6 b. For example, the "transmission pair located in each direction of 0 °, 90 °, and 180 ° means a transmission pair in which the transmission tooth 6a is located in each direction of 0 °, 90 °, and 180 °. The relationship is the same in other angles. Since the recess 6b is provided in the flexible gear portion 20 having flexibility, the recess is shifted from the corresponding transmission tooth 6a by a range of-2 degrees to +2 degrees depending on the state of the transmission pair.

In addition, the plurality of transfer pairs may not be arranged at equal intervals in the circumferential direction as long as the first pair 61 and the second pair 62 can be created. In this case, from the viewpoint of stably rotating the output unit 40, it is preferable to minimize the moment of inertia about the axis AX by matching the center of gravity of the entire output unit 40 provided with the plurality of transmission teeth 6a with the axis AX.

In the harmonic gear device 100, the first annular portion 22 of the flexible gear portion 20 and the second annular portion 41 of the output portion 40 are located between the support portion 50 and the cam portion 12. This can shorten the distance in the axial direction from the rotating input element to the output element. As a result, each structure can be made compact in the axial direction, and the harmonic gear device 100 can be configured to be small. In addition, when the distance in the axial direction from the rotating input element to the output element is short, it is difficult to apply stress in a direction inclined with respect to the axis AX to the flexible gear portion 20 and the internal gear portion 30 that are engaged with each other. As a result, one tooth tip of the flexible gear portion 20 and the inner gear portion 30 can be brought into contact with the other tooth bottom in the axial direction, and abrasion of the gears can be suppressed.

In the harmonic gear device 100, not only the cam portion 12 but also the flexible gear portion 20 and the output portion 40 are hollow in the shape of a ring as viewed from the axial direction. Therefore, a space through which wiring and the like pass can be ensured inside the device. Further, since the output side end of the flexible gear portion 20 is not closed, the flexibility of the flexible gear portion 20 can be maintained while ensuring the wall thickness of the flexible gear portion 20 to some extent. Therefore, the flexible gear portion 20 can be made to have good resistance to buckling, and is less likely to be broken. The thickness of the flexible gear portion 20 is not limited, but may be set to a range of 0.5 to 1mm, for example. In addition, the flexible gear portion 20 is in a bottomless cylindrical shape, and thus is easy to process. In principle, according to the harmonic gear device 100, the backlash can be eliminated and the idle rotation can be minimized.

In addition, according to the harmonic gear device 100, the number of poles of the cam portion 12 is not only n=2, but also a change of n+.3 can be provided, and therefore the following advantages are also provided. First, consider a case where the cam portion 12 of the harmonic generation portion 10 is set to an elliptical shape (n=2). When the pitch circle diameter of the internal gear portion 30 is set to D and the pitch circle diameter of the flexible gear portion 20 is set to D, the reduction ratio i can be regarded as "i= (T-T)/t=2/T" or "i= (D-D)/D". Then, in order to reduce the value of the reduction ratio i (obtain a rotational output after further deceleration), it is necessary to increase the number of teeth t or the ratio of the diameter D of the flexible gear portion 20 to the diameter D of the internal gear portion 30. On the other hand, in order to increase the value of the reduction ratio i (suppress the degree of reduction of the rotational output), it is necessary to reduce the number of teeth t or the ratio of the diameter D of the flexible gear portion 20 to the diameter D of the internal gear portion 30. Thus, when the elliptical cam portion 12 is used alone, various restrictions are imposed on the size and condition of the device, and it is difficult to achieve all reduction ratios.

On the other hand, even if at least one of the number of teeth T of the internal gear portion 30 and the number of teeth T of the flexible gear portion 20 is kept constant according to the change in the number of poles n+.3 of the cam portion 12, it is known that the value of the reduction ratio can be increased only by increasing the number of poles, and the value of the reduction ratio can be decreased only by decreasing the number of poles, according to the reduction ratio i=n/T. In addition to the change in the number of poles, setting the number of teeth T and changing the diameters of the flexible gear portion 20 and the internal gear portion 30 can realize a reduction ratio which is substantially infinitely variable.

The present disclosure is not limited to the above embodiments and drawings. Changes (including deletion of constituent elements) can be appropriately applied within a range that does not change the gist of the present disclosure. A modification of the harmonic gear device 100 after a part of the structure is deformed will be described below.

Modification 1

As in modification 1 shown in fig. 7, the output unit 40 may be located on the outer peripheral side of the flexible gear unit 20. In this case, the second annular portion 41 of the output portion 40 is located on the outer peripheral side of the first annular portion 22 of the flexible gear portion 20. The transmission teeth 6a fixed to the second annular portion 41 extend toward the axis AX, and are inserted into the recess 6b provided in the first annular portion 22. In fig. 7, the outer peripheral side of the flexible gear portion 20 and the output portion 40 as viewed from the axis direction is a diagram showing the relative displacement of the transmission teeth 6a and the concave portions 6b in the range of 0 ° to 180 ° when the cam portion 12 having the number of poles n=2 rotates about the axis AX according to the operation of the motor 213. In modification 1, the number and function of the transmission pairs as the pair of transmission teeth 6a and the concave portion 6b can be considered in the same manner as in the foregoing embodiment.

Modification 2

In the above embodiment and modification 1, the example in which the transmission teeth 6a are projected in the same width and the recesses 6b are recessed in the same width has been shown, but the shapes of the transmission portions 6a and the recesses 6b are not limited and can be arbitrarily changed. For example, as in modification 2 shown in fig. 8, the transmission teeth 6a may have a tapered shape that tapers toward the concave portion 6b, and the concave portion 6b may be formed by a tapered recess corresponding to the transmission portion 6 a.

In the above, the example in which the transmission teeth 6a are provided in the second annular portion 41 and the concave portions 6b are provided in the first annular portion 22 has been described, but the relationship may be reversed. That is, when the element between the adjacent concave portions 6b is understood as a transmission tooth and the element between the adjacent transmission teeth 6a is understood as a concave portion, it is possible to represent that the concave portion is provided in the second annular portion 41 and the transmission tooth is provided in the first annular portion 22. Using this expression, the number and function of pairs of transfer teeth and recesses can be considered as in the foregoing embodiment. In this expression, the plurality of transmission pairs are so-called "arranged at equal intervals in the circumferential direction" as long as a plurality of transmission teeth corresponding to each other are inserted into a plurality of recesses arranged at equal intervals in the circumferential direction, for example.

In the above, the example in which the harmonic gear device 100 is assembled to the robot 200 including the vertical multi-joint robot is shown, but not limited thereto. The harmonic gear device 100 can be incorporated into various robots such as a horizontal multi-joint robot and a Delta robot. The device to which the harmonic gear device 100 is assembled is not limited to a robot, and any device may be used as long as it is a device that obtains a rotational output that is decelerated at a desired reduction ratio with respect to a rotational input. The harmonic gear device 100 may be incorporated into, for example, precision machines other than robots, interesting articles, home appliances, vehicle-mounted components, and the like.

The number of teeth T of the flexible gear portion 20 and the number of teeth T of the internal gear portion 30 are arbitrary as long as T > T. However, when the number of poles of the cam portion 12 is N, it is preferable to set the relationship between the number of teeth T and the number of teeth T to "t=t+n".

The material of the members constituting the harmonic gear device 100 is arbitrary, and not limited to metal, and engineering plastics, resins, ceramics, and the like can be appropriately selected according to the purpose.

(1) The harmonic gear device 100 described above has a pair of transmission teeth 6a and concave portions 6b, that is, a transmission pair, as a structure for transmitting the power of the flexible gear portion 20 to the output portion 40. The width of the recess 6b in the circumferential direction is wider than the width of the transmission tooth 6a in the circumferential direction, allowing the relative displacement of the flexible gear portion 20 and the output portion 40 in the circumferential direction. With this configuration, as described above, unnecessary stress mainly applied to the flexible gear portion 20 can be suppressed, and therefore the harmonic gear device 100 is less likely to be broken.

Further, the flexible gear portion 20 has a first annular portion 22 formed integrally with the external gear 21 from the same material as the external gear 21. Therefore, the structure is simple. Further, the flexible gear portion 20 can be manufactured at one time by, for example, cutting, and the flexible gear portion 20 is easy to manufacture because it includes not only the external gear 21 but also the first annular portion 22 as a portion that transmits force to the output portion 40.

In addition, in the harmonic gear device 100 of the present disclosure, the flexible gear portion 20 and the output portion 40 rotate together. That is, even if the cam portion 12 rotates, the transmission teeth 6a inserted into one of the concave portions 6b do not move to the adjacent concave portion 6b, and the engagement relationship between the transmission teeth 6a and the concave portion 6b constituting 1 transmission pair is maintained. The flexible gear portion 20 of the present disclosure constitutes a gear mechanism as follows: the external gear 21 rotates while being offset from the meshing position with the internal gear 31 with respect to the internal gear portion 30, while the first annular portion 22 rotates while being engaged with the second annular portion 41 of the output portion 40. This is a large difference from the double-type harmonic gear device described above, which corresponds to the shift in the meshing position between the external gear of the flexible gear portion 20 and the gear provided in the output element. As described above, with the harmonic gear device 100 that maintains the engagement relationship between the transmission teeth 6a and the concave portions 6b, there is less possibility that the relative position of the flexible gear portion 20 and the output element will deviate from the desired position, as compared to the duplex harmonic gear device.

In addition, when N is arbitrarily set as the number of poles, various reduction ratios can be realized with a simple structure.

(2) The number of transfer pairs may be 2×n or more, and may be arranged at equal intervals in the circumferential direction. According to this configuration, the output points at which the force is transmitted from the flexible gear portion 20 to the output portion 40 can be uniformly dispersed in the circumferential direction, and therefore the output portion 40 can be rotated with high torque. The transfer pair may be 4×n or more, or may be a fixed number (for example, 16) irrespective of the number of poles N.

(3) The plurality of transmission pairs include transmission pairs that satisfy the condition of the first pair 61 and the second pair 62 when the cam portion 12 rotates about the axis AX. With this configuration, as described above, the force in the circumferential direction can be efficiently transmitted from the flexible gear portion 20 to the output portion 40.

(4) Preferably, the first pair 61 is N and the second pair 62 is N.

(5) Preferably, the first pair 61 and the second pair 62 are alternately present every 360 °/(2×n) at an angle centered on the axis AX.

(6) Of the N transmission pairs, at least at positions corresponding to the poles of the cam portion 12, the transmission teeth 6a are separated from the recesses 6b in the radial direction. Further, the first annular portion 22 allows displacement in the radial direction with respect to the second annular portion 41. With this configuration, the relative displacement between the flexible gear portion 20 and the output portion 40 in the radial direction can be absorbed, and therefore, the unnecessary stress can be reduced more favorably.

(7) The diameter of the first annular portion 22 is smaller than the diameter of the external gear 21. The flexible gear portion 20 further includes a connecting portion 23, and the connecting portion 23 connects the external gear 21 and the first annular portion 22, and is integrally formed with the external gear 21 and the first annular portion 22 from the same material as the external gear 21 and the first annular portion 22. With this structure, the space existing on the outer peripheral side of the first annular portion 22 can be effectively utilized. Further, the flexible gear portion 20 can be manufactured at one time by, for example, cutting, and the flexible gear portion 20 is provided with the external gear 21, the first annular portion 22, and the connecting portion 23, so that the manufacturing is easy.

(8) As shown in fig. 4, according to the structure in which the second annular portion 41 is located on the inner peripheral side of the first annular portion 22, the harmonic gear device 100 can be prevented from being enlarged in the radial direction.

(9) As shown in fig. 7, according to the configuration in which the second annular portion 41 is located on the outer peripheral side of the first annular portion 22, a space through which wiring and the like pass can be ensured in the vicinity of the axis AX of the harmonic gear device 100.

(10) The first annular portion 22 and the second annular portion 41 are located between the support portion 50 and the cam portion 12. According to this configuration, as described above, the length in the axial direction from the cam portion 12 to the output point of the flexible gear portion 20 can be suppressed, and each configuration can be made compact in the axial direction, so that the harmonic gear device 100 can be configured in a small size.

The internal gear portion 30 further includes: an insertion hole 32 into which the screw 82 is inserted; and a determining portion 33 located between the insertion hole 32 and the first annular portion 22. The portion of the determining portion 33 facing the outer ring 51 in the axial direction has an annular groove 33a centered on the axis AX. An O-ring 72 is fitted into the annular groove 33a. Here, in the harmonic gear device 100, the power of the flexible gear portion 20 is transmitted to the output portion 40 by the engagement of the first annular portion 22 and the second annular portion 41, and no fixing member such as a pin or a screw for fixing the flexible gear portion 20 to the output portion 40 is provided. In the case where the fixing member is provided in the radial direction, the determining portion 33 narrows in the radial direction. However, according to the above harmonic gear device 100, since the fixing member is not required, the arrangement space of the determination unit 33 in which the O-ring 72 is fitted can be ensured. Therefore, the sealing function is not impaired.

The support portion 50 is not limited to a cross roller bearing, and may be a ball bearing, a bearing that supports the output portion 40 so as to be slidable and rotatable, or the like.

The present invention is capable of various embodiments and modifications without departing from the broad spirit and scope of the invention. The above-described embodiments are illustrative examples for explaining the present invention, and do not limit the scope of the present invention. That is, the scope of the present invention is not represented by the embodiments, but by the scope of the patent claims. Further, various modifications performed within the scope of the patent claims and the meaning of the invention equivalent thereto are regarded as being within the scope of the invention.

In the above description, descriptions of well-known technical matters are omitted as appropriate for easy understanding of the present disclosure.

(symbol description)

100 … harmonic gear device

10 … harmonic generation part, AX … axis

11 … cylindrical shaft portion, 12 … cam portion, 13 … wave bearing

20 … flexible gear portion

21 … external gear, 22 … first annular part, 23 … connecting part

30 … internal gear portion

31 … internal gear, 32 … insertion hole, 33 … determination part, 33a … annular groove

40 … output part

41 … second annular portion, 42 … supported portion

50 … support part

51 … outer ring and 52 … inner ring

6a … transfer teeth, 6b … recesses, 61 … first pair, 62 … second pair

72 … O-ring.

Claims

1. A harmonic gear device, characterized in that the harmonic gear device comprises:

2. The harmonic gear device according to claim 1, wherein,

the transfer pairs are 2×n or more and are arranged at equal intervals in the circumferential direction.

3. The harmonic gear device according to claim 1 or 2, wherein,

the plurality of said transfer pairs comprises:

when the cam portion rotates about the axis, the transmission teeth are located in a first pair of one ends of the recess in the circumferential direction and in a second pair of the other ends of the recess in the circumferential direction.

4. The harmonic gear device according to claim 3, wherein,

the first pair is N, and the second pair is N.

5. The harmonic gear device according to claim 4, wherein,

the first pair and the second pair are alternately present every 360 °/(2×n) at an angle centered on the axis.

6. The harmonic gear device according to any one of claims 1 to 5, wherein,

of the plurality of transmission pairs, at least N transmission pairs located at positions corresponding to the poles of the cam portion, the transmission teeth are separated from the recess in the radial direction,

the first annular portion allows displacement in the radial direction relative to the second annular portion.

7. The harmonic gear device according to any one of claims 1 to 6, wherein,

the diameter of the first annular portion is smaller than the diameter of the external gear,

the flexible gear portion has a connecting portion that connects the external gear with the first annular portion and is integrally formed with the external gear and the first annular portion from the same material as the external gear and the first annular portion.

8. The harmonic gear device according to any one of claims 1 to 7, wherein,

the second annular portion is located on an inner peripheral side of the first annular portion.

9. The harmonic gear device according to any one of claims 1 to 7, wherein,

the second annular portion is located on an outer peripheral side of the first annular portion.

10. The harmonic gear device according to claim 8, wherein,

the harmonic gear device further includes a support portion that supports the output portion so as to be rotatable with respect to the internal gear portion,

the first annular portion and the second annular portion are located between the support portion and the cam portion,

the support section is provided with: an outer ring fixed to the inner gear portion by a screw extending in the axial direction; and an inner ring fixed to the output portion,

The internal gear portion includes:

an insertion hole formed along the axial direction for insertion of the screw; and

a determining portion located between the insertion hole and the first annular portion,

the portion of the determining portion facing the outer ring in the axial direction has an annular groove centered on the axis,

an O-ring is inserted into the annular groove.